arch/parisc/lib/checksum.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              MIPS specific IP/TCP/UDP checksumming routines
   7  *
   8  * Authors:     Ralf Baechle, <ralf@waldorf-gmbh.de>
   9  *              Lots of code moved from tcp.c and ip.c; see those files
  10  *              for more names.
  11  *
  12  *              This program is free software; you can redistribute it and/or
  13  *              modify it under the terms of the GNU General Public License
  14  *              as published by the Free Software Foundation; either version
  15  *              2 of the License, or (at your option) any later version.
  16  *
  17  * $Id: checksum.c,v 1.3 1997/12/01 17:57:34 ralf Exp $
  18  */
  19 #include <linux/module.h>
  20 #include <linux/types.h>
  21
  22 #include <net/checksum.h>
  23 #include <asm/byteorder.h>
  24 #include <asm/string.h>
  25 #include <asm/uaccess.h>
  26
  27 #define addc(_t,_r)                     \
  28         __asm__ __volatile__ (          \
  29 "       add             %0, %1, %0\n"   \
  30 "       addc            %0, %%r0, %0\n" \
  31         : "=r"(_t)                      \
  32         : "r"(_r), "0"(_t));
  33
  34 static inline unsigned short from32to16(unsigned int x)
  35 {
  36         /* 32 bits --> 16 bits + carry */
  37         x = (x & 0xffff) + (x >> 16);
  38         /* 16 bits + carry --> 16 bits including carry */
  39         x = (x & 0xffff) + (x >> 16);
  40         return (unsigned short)x;
  41 }
  42
  43 static inline unsigned int do_csum(const unsigned char * buff, int len)
  44 {
  45         int odd, count;
  46         unsigned int result = 0;
  47
  48         if (len <= 0)
  49                 goto out;
  50         odd = 1 & (unsigned long) buff;
  51         if (odd) {
  52                 result = be16_to_cpu(*buff);
  53                 len--;
  54                 buff++;
  55         }
  56         count = len >> 1;               /* nr of 16-bit words.. */
  57         if (count) {
  58                 if (2 & (unsigned long) buff) {
  59                         result += *(unsigned short *) buff;
  60                         count--;
  61                         len -= 2;
  62                         buff += 2;
  63                 }
  64                 count >>= 1;            /* nr of 32-bit words.. */
  65                 if (count) {
  66                         while (count >= 4) {
  67                                 unsigned int r1, r2, r3, r4;
  68                                 r1 = *(unsigned int *)(buff + 0);
  69                                 r2 = *(unsigned int *)(buff + 4);
  70                                 r3 = *(unsigned int *)(buff + 8);
  71                                 r4 = *(unsigned int *)(buff + 12);
  72                                 addc(result, r1);
  73                                 addc(result, r2);
  74                                 addc(result, r3);
  75                                 addc(result, r4);
  76                                 count -= 4;
  77                                 buff += 16;
  78                         }
  79                         while (count) {
  80                                 unsigned int w = *(unsigned int *) buff;
  81                                 count--;
  82                                 buff += 4;
  83                                 addc(result, w);
  84                         }
  85                         result = (result & 0xffff) + (result >> 16);
  86                 }
  87                 if (len & 2) {
  88                         result += *(unsigned short *) buff;
  89                         buff += 2;
  90                 }
  91         }
  92         if (len & 1)
  93                 result += le16_to_cpu(*buff);
  94         result = from32to16(result);
  95         if (odd)
  96                 result = swab16(result);
  97 out:
  98         return result;
  99 }
 100
 101 /*
 102  * computes a partial checksum, e.g. for TCP/UDP fragments
 103  */
 104 /*
 105  * why bother folding?
 106  */
 107 __wsum csum_partial(const void *buff, int len, __wsum sum)
 108 {
 109         unsigned int result = do_csum(buff, len);
 110         addc(result, sum);
 111         return (__force __wsum)from32to16(result);
 112 }
 113
 114 EXPORT_SYMBOL(csum_partial);
 115
 116 /*
 117  * copy while checksumming, otherwise like csum_partial
 118  */
 119 __wsum csum_partial_copy_nocheck(const void *src, void *dst,
 120                                        int len, __wsum sum)
 121 {
 122         /*
 123          * It's 2:30 am and I don't feel like doing it real ...
 124          * This is lots slower than the real thing (tm)
 125          */
 126         sum = csum_partial(src, len, sum);
 127         memcpy(dst, src, len);
 128
 129         return sum;
 130 }
 131 EXPORT_SYMBOL(csum_partial_copy_nocheck);
 132
 133 /*
 134  * Copy from userspace and compute checksum.  If we catch an exception
 135  * then zero the rest of the buffer.
 136  */
 137 __wsum csum_partial_copy_from_user(const void __user *src,
 138                                         void *dst, int len,
 139                                         __wsum sum, int *err_ptr)
 140 {
 141         int missing;
 142
 143         missing = copy_from_user(dst, src, len);
 144         if (missing) {
 145                 memset(dst + len - missing, 0, missing);
 146                 *err_ptr = -EFAULT;
 147         }
 148
 149         return csum_partial(dst, len, sum);
 150 }
 151 EXPORT_SYMBOL(csum_partial_copy_from_user);